622 research outputs found
Gaspra's Cratering Record.
No full textThe images of the asteroid 951 Gaspra obtained by Galileo show impact craters down to the resolution limit of 50m/pixel. The observed crater population has characteristics which very much resemble those seen on the inner solar system planets. The remarkable finding is that the distribution is steep. The cumulative size-frequency distribution can be approximated by a power law with an exponent (population index) of between -3.3 and -3.7 in the size range 200m to 800m. This is very close to the distribution characteristics found on the Earth's moon, on Mars, and on Mercury with population indices (cumulative) around -3.5 in that size range. At larger sizes (Dɣkm) there appears to be a slight flattening similar to what is found for distributions on the inner solar system objects. The lunarcurve(standard distribution, cf. Neukum et al., 1975) can be approximates very well to the Gaspra distribution taking into account the differences in the impact velocity and surface gravity conditions. A steep curve was expected for the asteroid belt cratering record (cf. Neukum 1983) if the cratering record in the inner solar system is directly linked to this region in terms of a source region. The findings on Gaspra support the view long held by the first author that (1) the small craters(D<1km) on the inner solar system bodies are essentially primary impact craters and not caused by "background secondaries", and (2) the inner solar system cratering is due to the bombardement by one and the same family of bodies derived from the asteroid belt. The time dependence of the cratering ratein the asteroid belt and in the inner solar system may have been quite different. If Gaspra is between 200 and 500 m.y. old as estimated in combining the crater frequency measurement with impact probability data derives from astronomical observations of large-size asteroids, then it appears impossible that the time
Hazard analysis and mapping. In: Zwahlen, F. (Ed.), Vulnerability and Risk Mapping for the Protection of Carbonate (karst) Aquifers
No full textThe ADAS Inner Solar System Project
No full textADAS, the Asiago-DLR Asteroid Survey, is a joint program between the Department of Astronomy and Astronomical Observatory of Padova and the DLR Berlin, dedicated to the search of asteroids. The observations are made with a 67/92cm Schmidt Telescope on Cima Ekar, near Asagio, in northern Italy. A 2Kx2K CCD camera provided by the DLR is in use, mostly in Time Delay Integration mode. The camera has a field of 0.67 square degrees and can reach a limiting magnitude V ~ 21.0 in 2 minutes of exposure time. Specific search programs, in particular for objects permanently inside the orbit of the Earth (IEOs), have been started. A simulation of the performance of the IEO survy based on the model population from Bottke at al. shows that the discovery of a one-digit number of IEOs may be possible with the layout and equipment of the ADAS survey within a couple of years of operation
Geological evolution of the Tyras Vallis paleolacustrine system, Mars
No full textUsing the new High Resolution Stereo Camera (HRSC) data and other Martian data sets, we reconstructed the hydrological history of an unnamed complex crater in the Xanthe Terra region. The crater hosted a lacustrine basin fed by a dense and centripetal drainage system, developed along its inner rim, and by the Tyras Vallis channel. Where the Tyras Vallis opens into the crater, a prominent delta-like feature is visible, characterized by a central terrace and two small longitudinal scarps. This deposit has been
used as sedimentary recorder of the crater lake history and allowed assessment of the overall hydrological evolution. Two major stands of the water level have been inferred at 700 and 550 m above the crater floor, based on the correlation between the morphology and topography of the fan and the crater floor deposits. Our reconstruction reveals a complex sedimentary evolution of the fan, which underwent deltaic and alluvial sedimentation, as a result of the different lake water levels and Tyras Vallis supplies. A dominant erosional evolution of the fan-delta was determined by the interaction between the fluvial characteristics and basin wave regime. Wave height analysis and morphological comparison with terrestrial analogues support this hypothesis. The lacustrine activity
could be chronologically placed between the Late Noachian and the Hesperian. The climatic conditions could have allowed the recharge of the regional groundwater system by precipitation and episodic fluvial activity. However, also heating effects of cratering could have affected the system, rejuvenating or accelerating the recharge of the
local aquifer
The ADAS inner solar system project
No full textADAS, the Asiago-DLR Asteroid Survey, is a joint program between the Department of Astronomy and Astronomical Observatory of Padova and the DLR Berlin, dedicated to the search of asteroids. The observations are made with a 67/92 cm Schmidt Telescope on Cima Ekar, near Asiago, in northern Italy. A 2K×2K CCD camera provided by the DLR is in use, mostly in Time Delay Integration mode. The camera has a field of 0.67 square degrees and can reach a limiting magnitude V ∼ 21.0 in 3 minutes of exposure time. Specific search programs, in particular for objects permanently inside the orbit of the Earth (IEOs), have been started. A simulation of the performance of the IEO survey based on the model population from Bottke et al. shows that the discovery of a one-digit number of IEOs may be possible with the layout and equipment of the ADAS survey within a couple of years of operation
De marasmo senili sive marcore naturali
No full textquam ... pro summis in medicina honoribus & privilegiis doctoralibus rite obtinendis, publico eruditorum examini subiicit Georg. Michael Neukum Scaphusio-Helvetus. Ad diem 10. Iulii, M D C C XLIII. ...Enthält 25 ThesenDiss. med. Basel, 174
Operational Processing of MEX HRSC Data
No full textThe HRSC onboard Mars Express is a multi-line pushbroom scanner which provides image data from 5 panchromatic stereo channels and 4 spectral bands (Neukum et al, 2004). A completely automated ground data processing line has been developed in the past years and is being applied on a routine base for each MEX orbit. It comprises the conversion of the original data stream transmitted to ground to de-compressed data (Level-1 data), the radiometric correction of the image data based on calibration information (Level-2 data) combined with orbit and pointing information for each image line, and a first rectification to standard scales of up to 12.5 m/pixel (Level-3 data) using a-priori topography information as defined by the MGS MOLA instrument. Level-2 and Level-3 data of HRSC's Super Resolution Channel (SRC) in scales of up to 2.5 m/pixel complete the HRSC capabilities. Thus, Level-2 and Level-3 are ready for distribution to the HRSC Co-Investigator
team within one day after data acquisition.
A standard Level-4 generation is started after completion of Level-2 data in order to derive HRSC digital terrain models in a standard 200 m grid. These DTMs are finally used for the generation of orthoimages of all 4 spectral bands and the high-resolution nadir channel. This standardized processing provides 3D and image data products within a few days after data acquisition for first science analyses. Based on nominal pointing and reconstructed orbit information the standard Level-4 data products comprise a mean absolute accuracy of a few hundred meters for planimetry and of better than 100 m for height.
Reference:
Neukum, G., Jaumann, R. and the HRSC Co-Investigator Team, 2004. HRSC: The High
Resolution Stereo Camera of Mars Express. ESA Special Publications SP-1240
Replication Data for: Slopes of Lunar Crater Size-Frequency Distributions at Copernican-Aged Craters
No full textAbstract
Craters on the lunar surface can provide valuable information about the timing and sequence of surface-forming processes on the Moon. A commonly used method for age determination is the analysis of the crater size-frequency distribution (CSFD) to which a production function (PF) is fitted that represents the size-frequency distribution of the impactors. However, the commonly used PF of Neukum (1983) is valid for crater diameters between 10 m and 300 km. Neukum et al. (2001, https://doi.org/10.1007/978-94-017-1035-0_3) revised the PF for crater diameters of 100 m–200 km. However, it is suggested to also be valid for the diameter range of 10 m–300 km as well. To assess whether we can extend a PF to craters ≤10 m in diameter, we investigated the slopes of the CSFDs of small craters formed on ejecta of young Copernican-aged craters Giordano Bruno, Moore F, North Ray, and South Ray. A PF for smaller diameters would allow dating of young geological units, which are typically small, and would reduce the statistical error in age determinations, since smaller craters are more abundant. However, small craters are strongly influenced by geological factors, such as target properties, crater degradation, and secondary craters. For craters between 10 and 20 m we obtain a steeper CSFD slope than Neukum's proposed −3 slope (cumulative), whereas for craters ≤10 m the slope is about −3. We conclude that the PF of Neukum (1983) provides a reasonable CSFD slope for smaller craters, although it was not developed for this crater diameter range.
Key Points
* We studied small craters on young ejecta blankets to evaluate if the lunar production function (PF) is viable for craters ≤10 m
* The crater size-frequency distributions (CSFDs) indicate that the PF can indeed be extended to crater diameters ≤10 m
* Our observed slopes of CSFDs at the studied Copernican-aged craters are consistent with previous finding
Forecasting LULC change and its impact on urban hydrology and urban flood mitigation under climate variability
No full textThis study aimed to analyse and assess the impacts of land-use land-cover change and climate variability on the urban hydrology of the catchment. The rapid urbanisation and increase in population in the cities alter the local hydrology of the area. This urbanisation demands massive infrastructure and changes the nature of the city's livelihood. Therefore, a rapid increase in urban settlements and informal growth of the built-up area has been witnessed. This affects the surface imperviousness and local climatic condition caused by the increase in urban heat. Therefore, this study has been conducted to analyse and evaluate how urbanisation and population growth impact the local hydrology of the Raipur city. The study area is a part of the newly constituted Chhattisgarh state, formed in year 2000 and recently planned to develop a new smart city. In this context, Raipur city in India was selected. Raipur city is one of India's most important, highly populated, industrialised, economically strong and rapid growing cities. The city is located in India's one of the popular watersheds in central river basin, the Mahanadi basin. It is characterised by substantial population growth and rapid sprawl of urban areas, industrialisation, and irrigation areas and facilities for meeting the increasing water demand. In response, climate variability changes the study area's precipitation regime and trends of climatic variables. There is no such comprehensive study, documentation and literature related to the impact of LULC change and climate variability on water management in Raipur is available. Therefore, it is urgent to study the impact of future land-use land-cover change on Raipur city's hydrology and analyse whether and to which degree the consequences of this change put the area at risk for water management. Hence, an attempt is made to analyse and evaluate the associated phenomenon by using the following methodologies: assessment of LULC change for year 1988-2018 and forecasting LULC for future three decades (2028-2048) is performed using the Machine Learning Techniques. Maximum-Likelihood-Classifier was used to perform supervised classification of satellite images. Then multi-layer perceptron with the Markov-chain method was utilised to assess the transition probability matrix to forecast the future LULC. The effect of LULC change on land surface temperature (LST) has been analysed using the temperature band of Landsat satellite data. Similarly, normalised indices NDVI, NDBI, and NDWI was calculated to analyse the vegetation cover, building cover and water cover change in the area and correlated with the calculated LST. Later the impact of LULC on LST and LST on rainfall frequency was studied. Statistical Parametric change point tests and non-parametric trend tests were applied on the monthly, annual, and seasonal scale of the meteorological data. The results of these tests were used to prepare the different climatic scenarios for the catchment. Various Intensity-Duration-Frequency (IDF) were developed. Rainfall frequency analysis was performed on shorter duration rainfall to prepare the design storm events. To access the impact of LULC in the catchment, continuous hydrologic modeling using SWAT was modelled. Difference hydrologic components was modeled with the parametrisation of pre-developed methods. Similarly, a stormwater management model was prepared to identify suitable design rainfall. Time of concentration verses storm duration was plotted and result were analysed. The outcome of the analysis of LULC change and forecasted LULC shows that the built-up area of the catchment increases rapidly resulting increase in the curve number and imperviousness. Hydrological modeling results shows increase in surface runoff up to 30%, and groundwater percolation reduces up to 60% until the end of the year 2048. Assessment of LST shows the mean temperature in the city is increasing, and an island of heat is detected. Application of change-point method in the meteorological data has been conducted from the year 1971-2020 which results the year 1993 as a change point. To check the validity of change-point test results trend analysis was applied and it’s result reveals rising trends in annual Maximum temperature, Minimum temperature, relative humidity and rainfall while the falling trend in annual wind speed, evaporation and sunshine hour. From the observation, the temperature was found as the main factor causing the effect of changing rainfall pattern. This rise in minimum and maximum temperature may be caused due to urbanization, increasing industrialization and climate change late after 1993. The results of frequency analysis reveal that the trend in rainfall pattern has been changed. Therefore, IDF was recalculated based on existing climatic conditions. Different return period IDF was developed and suitable design storm was computed using the results of Gumbel Extreme Value-I (GEV-I) distribution which is found best for this study area. The existing storm water drainage infrastructure in Raipur is not sufficient to handle the design storm. Therefore, 2D hydro-dynamic flood inundation model in SWMM was developed and analysed. The results of SWMM show that many of locations in the city are vulnerable to flooding. To mitigate the flooding suitable LIDs strategy was proposed in the SWMM model. The results show a significant decrease in flooding and minimises 60% of sheet flow. If suggested LID were applied in the city, 30% of the storm runoff could be directly stored in the groundwater. Subjected to this would be an alarming situation for the water management in Raipur city in the near future. The overall methodology of this study may also be applied in similar geographical regions to assess the impact of LULC change and its impact on the hydrological condition of the catchment. Moreover, the hydro-climatological outcome of this study may be further utilized to analyse climate variability and to mitigate flood situations caused due to unavailability of design storms
- …
